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Sep 22, 2013
09/13

by
S. W. Zhang; L. Ma; Y. D. Hou; J. S. Zhang; T. L. Xia; G. F. Chen; J. P. Hu; G. M. Luke; W. Yu

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We performed $^{75}$As NMR studies on two overdoped high-quality Ba$_{1-x}$K$_{x}$Fe$_2$As$_2$ (x=0.7 and 1.0) single crystals. In the normal states, we found a dramatic increase of the spin-lattice relaxation ($1/^{75}T_1$) from the x=0.7 to the x=1.0 samples. In KFe$_2$As$_2$, the ratio of $1/^{75}T_1TK_n^2$, where $^{75}K_n$ is the Knight shift, increases as temperature drops. These results indicate the existence of a new type of spin fluctuations in KFe$_2$As$_2$ which is accustomed to...

Source: http://arxiv.org/abs/0908.4369v2

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Sep 18, 2013
09/13

by
Georg Böcherer; Alexandre de Baynast

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WLAN is one of the most successful applications of wireless communications in daily life because of low cost and ease of deployment. The enabling technique for this success is the use of random access schemes for the wireless channel. Random access requires minimal coordination between the nodes, which considerably reduces the cost of the infrastructure. Recently, cooperative communication in wireless networks has been of increasing interest because it promises higher rates and reliability. An...

Source: http://arxiv.org/abs/0809.5204v2

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Sep 22, 2013
09/13

by
Ronan Le Guével; Jacques Lévy-Véhel

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The study of non-stationary processes whose local form has controlled properties is a fruitful and important area of research, both in theory and applications. We present here a construction of multifractional multistable processes, based on the Ferguson-Klass-LePage series representation of stable processes. We consider various particular cases of interest, including multistable L\'evy motion, multistable reverse Ornstein-Uhlenbeck process, log-fractional multistable motion and linear...

Source: http://arxiv.org/abs/0906.5042v2

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Sep 19, 2013
09/13

by
Raghunandan H. Keshavan; Sewoong Oh

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We consider the problem of reconstructing a low-rank matrix from a small subset of its entries. In this paper, we describe the implementation of an efficient algorithm called OptSpace, based on singular value decomposition followed by local manifold optimization, for solving the low-rank matrix completion problem. It has been shown that if the number of revealed entries is large enough, the output of singular value decomposition gives a good estimate for the original matrix, so that local...

Source: http://arxiv.org/abs/0910.5260v2

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Sep 23, 2013
09/13

by
Shi Pu; Sang-Jin Sin; Yang Zhou

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We build a holographic description of non-relativistic system for superconductivity in strongly interacting condensed matter via gauge/gravity duality. We focus on the phase transition and give an example to show that a simple gravitational theory can provide a non-relativistic holographical dual description of a superconductor. There is also a critical temperature like the relativistic case, below which a charged condensation field appears by a second order phase transition and the (DC)...

Source: http://arxiv.org/abs/0903.4185v3

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Sep 23, 2013
09/13

by
Su-Chan Park

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Although Hinrichsen in his unpublished work theoretically rebutted the possibility of the discontinuous transition in one-dimensional nonequilibrium systems unless there are additional conservation laws, long-range interactions, macroscopic currents, or special boundary conditions, we have recently observed the resurrection of the claim that the triplet creation model (TC) introduced by Dickman and Tom\'e [Phys. Rev. E {\bf 44}, 4833 (1991)] would show the discontinuous transition. By extensive...

Source: http://arxiv.org/abs/0903.3436v3

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Sep 19, 2013
09/13

by
Mikhail Lemeshko; Bretislav Friedrich

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We develop an analytic model of vector correlations in rotationally inelastic atom-diatom collisions and test it against the much examined Ar--NO ($\mathbf X^2 \Pi$) system. Based on the Fraunhofer scattering of matter waves, the model furnishes complex scattering amplitudes needed to evaluate the polarization moments characterizing the quantum stereodynamics. The analytic polarization moments are found to be in an excellent agreement with experimental results and with close-coupling...

Source: http://arxiv.org/abs/0910.0952v2

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Sep 21, 2013
09/13

by
Mirjam Cvetič; Iñaki García-Etxebarria; Robert Richter

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We study in detail the system of D6 branes and euclidean D2-brane instantons intersecting at angles in type IIA string theory. We find that in the absence of orientifolds the system does not contribute to the low energy superpotential, in agreement with expectations based on effective field theory arguments. We also comment on the implications of our results for dual string theory pictures.

Source: http://arxiv.org/abs/0905.1694v3

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Sep 22, 2013
09/13

by
Saad Zaheer; Sahand Jamal Rahi; Thorsten Emig; Robert L. Jaffe

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We investigate the electromagnetic Casimir interactions of an object contained within an otherwise empty, perfectly conducting spherical shell. For a small object we present analytical calculations of the force, which is directed away from the center of the cavity, and the torque, which tends to align the object opposite to the preferred alignment outside the cavity. For a perfectly conducting sphere as the interior object, we compute the corrections to the proximity force approximation (PFA)...

Source: http://arxiv.org/abs/0908.3270v2

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Sep 19, 2013
09/13

by
MIrna Dzamonja; Istvan Juhasz

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We give a construction under $CH$ of a non-metrizable compact Hausdorff space $K$ such that any uncountable semi-biorthogonal sequence in $C(K)$ must be of a very specific kind. The space $K$ has many nice properties, such as being hereditarily separable, hereditarily Lindel\"of and a 2-to-1 continuous preimage of a metric space, and all Radon measures on $K$ are separable. However $K$ is not a Rosenthal compactum. We introduce the notion of bidiscrete systems in compact spaces and note...

Source: http://arxiv.org/abs/0910.3091v2

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Sep 21, 2013
09/13

by
Stephen C. Anco; Amanullah Dar

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For the Euler equations governing compressible isentropic fluid flow with a barotropic equation of state (where pressure is a function only of the density), local conservation laws in $n>1$ spatial dimensions are fully classified in two primary cases of physical and analytical interest: (1) kinematic conserved densities that depend only on the fluid density and velocity, in addition to the time and space coordinates; (2) vorticity conserved densities that have an essential dependence on the...

Source: http://arxiv.org/abs/0902.3405v3

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Sep 22, 2013
09/13

by
Brian A. Munson; Ismar Volic

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We study the spaces of string links and homotopy string links in an arbitrary manifold using multivariable manifold calculus of functors. We construct multi-cosimplicial models for both spaces and deduce certain convergence properties of the associated Bousfield-Kan homotopy and cohomology spectral sequences when the ambient manifold is a Euclidean space of dimension four or more.

Source: http://arxiv.org/abs/0906.2589v3

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Sep 22, 2013
09/13

by
Eli Visbal; Abraham Loeb; Stuart Wyithe

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21cm emission from residual neutral hydrogen after the epoch of reionization can be used to trace the cosmological power spectrum of density fluctuations. Using a Fisher matrix formulation, we provide a detailed forecast of the constraints on cosmological parameters that are achievable with this probe. We consider two designs: a scaled-up version of the MWA observatory as well as a Fast Fourier Transform Telescope. We find that 21cm observations dedicated to post-reionization redshifts may...

Source: http://arxiv.org/abs/0812.0419v3

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Sep 22, 2013
09/13

by
Dan Coe; Leonidas Moustakas

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Future large ensembles of time delay lenses have the potential to provide interesting cosmological constraints complementary to those of other methods. In a flat universe with constant w including a Planck prior, LSST time delay measurements for ~4,000 lenses should constrain the local Hubble constant h to ~0.007 (~1%), Omega_DE to ~0.005, and w to ~0.026 (all 1-sigma precisions). Similar constraints could be obtained by a dedicated gravitational lens observatory (OMEGA) which would obtain...

Source: http://arxiv.org/abs/0906.4108v2

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Sep 20, 2013
09/13

by
D. Cohen; G. Denham; M. Falk; A. Varchenko

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If F is a master function corresponding to a hyperplane arrangement A and a collection of weights y, we investigate the relationship between the critical set of F, the variety defined by the vanishing of the one-form w = d log F, and the resonance of y. For arrangements satisfying certain conditions, we show that if y is resonant in dimension p, then the critical set of F has codimension at most p. These include all free arrangements and all rank 3 arrangements.

Source: http://arxiv.org/abs/0907.0896v2

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Sep 21, 2013
09/13

by
Maria Beltran; Dan Hooper; Edward W. Kolb; Zosia C. Krusberg

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Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated...

Source: http://arxiv.org/abs/0808.3384v2

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Sep 21, 2013
09/13

by
Kwang-Chang Lai; Guey-Lin Lin; T. C. Liu

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We discuss the reconstruction of neutrino flavor ratios at astrophysical sources through the future neutrino-telescope measurements. Taking the ranges of neutrino mixing parameters $\theta_{ij}$ as those given by the current global fit, we demonstrate by a statistical method that the accuracies in the measurements of energy-independent ratios $R\equiv\phi (\nu_{\mu})/(\phi (\nu_{e})+\phi (\nu_{\tau}))$ and $S\equiv\phi (\nu_e)/\phi (\nu_{\tau})$ among integrated neutrino flux should both be...

Source: http://arxiv.org/abs/0905.4003v3

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Sep 23, 2013
09/13

by
S. Mazoyer; F. Ebert; G. Maret; P. Keim

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We investigate the dynamics of a glass forming 2D colloidal mixture and show the existence of collective motions of the particles. We introduce a mean square displacement MSD with respect to the nearest neighbors which shows remarkable deviations from the usual MSD quantifying the individual motion of our particles. Combined with the analysis of the self part of the Van Hove function this indicates a coupled motion of particles with their cage as well as intra cage hopping processes.

Source: http://arxiv.org/abs/0903.4675v4

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Sep 21, 2013
09/13

by
Y. Zhou; J. H. Jiang; M. W. Wu

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We investigate electron spin relaxation in $p$-type GaAs quantum wells from a fully microscopic kinetic spin Bloch equation approach, with all the relevant scatterings, such as the electron-impurity, electron-phonon, electron-electron Coulomb, electron-hole Coulomb and electron-hole exchange (the Bir-Aronov-Pikus mechanism) scatterings explicitly included. From this approach, we examine the relative importance of the D'yakonov-Perel' and Bir-Aronov-Pikus mechanisms in wide ranges of...

Source: http://arxiv.org/abs/0905.2790v2

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Sep 21, 2013
09/13

by
Michal Hajdusek; Vlatko Vedral

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We present a closest separable state to cluster states. We start by considering linear cluster chains and extend our method to cluster states that can be used as a universal resource in quantum computation. We reproduce known results for pure cluster states and show how our method can be used in quantifying entanglement in noisy cluster states. Operational meaning is given to our method that clearly demonstrates how these closest separable states can be constructed from two-qubit clusters in...

Source: http://arxiv.org/abs/0902.4343v2

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Sep 19, 2013
09/13

by
Pramod Kumar Mishra

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Lattice model of directed self avoiding walk has been solved analytically to investigate adsorption desorption phase transition behaviour of a semiflexible sequential copolymer chain on a two dimensional impenetrable surface perpendicular to the preferred direction of the walk of the copolymer chain in three dimensions. The stiffness of the chain has been accounted by introducing an energy barrier for each bend in the walk of the copolymer chain. Exact value of adsorption desorption transition...

Source: http://arxiv.org/abs/0909.4653v3

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Sep 22, 2013
09/13

by
A. J. F. Hayes; H. L. Haselgrove; Alexei Gilchrist; T. C. Ralph

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We use a combination of analytical and numerical techniques to calculate the noise threshold and resource requirements for a linear optical quantum computing scheme based on parity-state encoding. Parity-state encoding is used at the lowest level of code concatenation in order to efficiently correct errors arising from the inherent nondeterminism of two-qubit linear-optical gates. When combined with teleported error-correction (using either a Steane or Golay code) at higher levels of...

Source: http://arxiv.org/abs/0908.3932v2

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Sep 22, 2013
09/13

by
Ertan Göklü; Claus Lämmerzahl

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Space--time can be understood as some kind of space--time foam of fluctuating bubbles or loops which are expected to be an outcome of a theory of quantum gravity. One recently discussed model for this kind of space--time fluctuations is the holographic principle which allows to deduce the structure of these fluctuations. We review and discuss two scenarios which rely on the holographic principle leading to holographic noise. One scenario leads to fluctuations of the space--time metric affecting...

Source: http://arxiv.org/abs/0908.3797v3

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Sep 22, 2013
09/13

by
Michael Herrmann; Jens D. M. Rademacher

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We consider infinite FPU-type atomic chains with general convex potentials and study the existence of monotone fronts that are heteroclinic travelling waves connecting constant asymptotic states. Iooss showed that small amplitude fronts bifurcate from convex-concave turning points of the force. In this paper we prove that fronts exist for any asymptotic states that satisfy certain constraints. For potentials whose derivative has exactly one turning point these constraints precisely mean that...

Source: http://arxiv.org/abs/0812.1712v2

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Sep 19, 2013
09/13

by
D. Eckert; V. Savchenko; N. Produit; C. Ferrigno

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Aims. We use the IBIS/ISGRI telescope on-board INTEGRAL to measure the position of the centroid of the 20-200 keV emission from the Crab region. Methods. We find that the astrometry of the IBIS telescope is affected by the temperature of the IBIS mask during the observation. After correcting for this effect, we show that the systematic errors in the astrometry of the telescope are of the order of 0.5 arcsec. In the case of the Crab nebula and several other bright sources, the very large number...

Source: http://arxiv.org/abs/0910.1698v2

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Sep 19, 2013
09/13

by
G. Tommei; A. Milani; D. Vokrouhlicky

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The radioscience experiment is one of the on board experiment of the Mercury ESA mission BepiColombo that will be launched in 2014. The goals of the experiment are to determine the gravity field of Mercury and its rotation state, to determine the orbit of Mercury, to constrain the possible theories of gravitation (for example by determining the post-Newtonian (PN) parameters), to provide the spacecraft position for geodesy experiments and to contribute to planetary ephemerides improvement. This...

Source: http://arxiv.org/abs/0910.5818v2

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Sep 23, 2013
09/13

by
Dachun Yang; Dongyong Yang; Yuan Zhou

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Let ${\mathcal X}$ be a space of homogeneous type in the sense of Coifman and Weiss and ${\mathcal D}$ a collection of balls in $\cx$. The authors introduce the localized atomic Hardy space $H^{p, q}_{\mathcal D}({\mathcal X})$ with $p\in (0,1]$ and $q\in[1,\infty]\cap(p,\infty]$, the localized Morrey-Campanato space ${\mathcal E}^{\alpha, p}_{\mathcal D}({\mathcal X})$ and the localized Morrey-Campanato-BLO space $\widetilde{\mathcal E}^{\alpha, p}_{\mathcal D}({\mathcal X})$ with...

Source: http://arxiv.org/abs/0903.4576v2

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Sep 19, 2013
09/13

by
A. Crisanti; C. De Dominicis; T. Sarlat

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The spin glass behavior near zero temperature is a complicated matter. To get an easier access to the spin glass order parameter $Q(x)$ and, at the same time, keep track of $Q_{ab}$, its matrix aspect, and hence of the Hessian controlling stability, we investigate an expansion of the replicated free energy functional around its ``spherical'' approximation. This expansion is obtained by introducing a constraint-field and a (double) Legendre Transform expressed in terms of spin correlators and...

Source: http://arxiv.org/abs/0909.2556v2

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Sep 19, 2013
09/13

by
Raghunandan H. Keshavan; Andrea Montanari; Sewoong Oh

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We consider a problem of significant practical importance, namely, the reconstruction of a low-rank data matrix from a small subset of its entries. This problem appears in many areas such as collaborative filtering, computer vision and wireless sensor networks. In this paper, we focus on the matrix completion problem in the case when the observed samples are corrupted by noise. We compare the performance of three state-of-the-art matrix completion algorithms (OptSpace, ADMiRA and FPCA) on a...

Source: http://arxiv.org/abs/0910.0921v2

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Sep 18, 2013
09/13

by
F. Ren; B. Zheng; P. Chen

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A dynamic herding model with interactions of trading volumes is introduced. At time $t$, an agent trades with a probability, which depends on the ratio of the total trading volume at time $t-1$ to its own trading volume at its last trade. The price return is determined by the volume imbalance and number of trades. The model successfully reproduces the power-law distributions of the trading volume, number of trades and price return, and their relations. Moreover, the generated time series are...

Source: http://arxiv.org/abs/0803.0844v4

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Sep 19, 2013
09/13

by
Federico I. Pelupessy; Padelis P. Papadopoulos

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We use time-varying models of the coupled evolution of the HI, H_2 gas phases and stars in galaxy-sized numerical simulations to: a) test for the emergence of the Kennicutt-Schmidt (K-S) and the H_2-pressure relation, b) explore a realistic H_2-regulated star formation recipe which brings forth a neglected and potentially significant SF-regulating factor, and c) go beyond typical galactic environments (for which these galactic empirical relations are deduced) to explore the early evolution of...

Source: http://arxiv.org/abs/0910.4905v2

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Sep 19, 2013
09/13

by
Alessandro Soncini; Liviu F. Chibotaru

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We investigate the spin transport through strongly anisotropic noncollinear magnetic molecules and find that the noncollinear magnetization acts as a spin-switching device for the current. Moreover, spin currents are shown to offer a viable route to selectively prepare the molecular device in one of two degenerate noncollinear magnetic states. Spin-currents can be also used to create a non-zero density of toroidal magnetization in a recently characterized Dy_3 noncollinear magnet.

Source: http://arxiv.org/abs/0910.5235v3

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Sep 23, 2013
09/13

by
Stefano Cardanobile; Stefan Rotter

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We introduce a nonlinear modification of the classical Hawkes process, which allows inhibitory couplings between units without restrictions. The resulting system of interacting point processes provides a useful mathematical model for recurrent networks of spiking neurons with exponential transfer functions. The expected rates of all neurons in the network are approximated by a first-order differential system. We study the stability of the solutions of this equation, and use the new formalism to...

Source: http://arxiv.org/abs/0904.1505v3

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Sep 19, 2013
09/13

by
Ricardo A. Mosna; Gustavo Marques Tavares

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We present a systematic study of spherically symmetric self-dual solutions of SU(2) Yang-Mills theory on Euclidean Schwarzschild space. All the previously known solutions are recovered and a new one-parameter family of instantons is obtained. The newly found solutions have continuous actions and interpolate between the classic Charap and Duff instantons. We examine the physical properties of this family and show that it consists of dyons of unit (magnetic and electric) charge.

Source: http://arxiv.org/abs/0909.5145v2

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Sep 18, 2013
09/13

by
John Brevik; Scott Nollet

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We compute the class groups of very general normal surfaces in complex projective three-space containing an arbitrary base locus $Z$, thereby extending the classic Noether-Lefschetz theorem (the case when $Z$ is empty). Our method is an adaptation of Griffiths and Harris' degeneration proof, simplified by a cohomology and base change argument. We give applications to computing Picard groups, which generalize several known results.

Source: http://arxiv.org/abs/0806.1243v3

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Oct 28, 2014
10/14

by
Staggs, Sarah E.; See, Mary Jean; Dubey, J P.; Villegas, Eric N.

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This article is from Journal of Visualized Experiments : JoVE . Abstract Toxoplasma gondii is an obligate intracellular protozoan pathogen that commonly infects humans. It is a well characterized apicomplexan associated with causing food- and water-borne disease outbreaks. The definitive host is the feline species where sexual replication occurs resulting in the development of the highly infectious and environmentally resistant oocyst. Infection occurs via ingestion of tissue cysts from...

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142894

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Sep 22, 2013
09/13

by
Kenzo Ishikawa; Yutaka Tobita

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Coherence lengths of one particle states described by quantum wave functions are studied. We show that one particle states in various situations are not described by simple plane waves but are described by wave packets that are superpositions of plane waves. Wave packet is an approximate eigenstate of the free Hamiltonian and has a finite spatial size which we call the coherence length. The coherence lengths in the coordinate space and in the momentum space are studied in the present paper. We...

Source: http://arxiv.org/abs/0906.3938v3

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Sep 21, 2013
09/13

by
S. Gupta; R. Kumar; R. P. Malik

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We demonstrate a few striking similarities and some glaring differences between (i) the free four (3 + 1)-dimensional (4D) Abelian 2-form gauge theory, and (ii) the anomalous two (1 + 1)-dimensional (2D) Abelian 1-form gauge theory, within the framework of Becchi-Rouet-Stora-Tyutin (BRST) formalism. We demonstrate that the Lagrangian densities of the above two theories transform in a similar fashion under a set of symmetry transformations even though they are endowed with a drastically...

Source: http://arxiv.org/abs/0905.0934v3

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Sep 20, 2013
09/13

by
Oscar J. C. Dias; Jose' P. S. Lemos

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We study in detail the quantum process in which a pair of black holes is created in a higher D-dimensional de Sitter (dS) background. The energy to materialize and accelerate the pair comes from the positive cosmological constant. The instantons that describe the process are obtained from the Tangherlini black hole solutions. Our pair creation rates reduce to the pair creation rate for Reissner-Nordstrom-dS solutions when D=4. Pair creation of black holes in the dS background becomes less...

Source: http://arxiv.org/abs/hep-th/0410279v3

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Sep 19, 2013
09/13

by
Christoph Lehner; Tilo Wettig

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We calculate the partition function of partially quenched chiral perturbation theory in the epsilon regime at next-to-leading order using the supersymmetry method in the formulation without a singlet particle. We include a nonzero imaginary chemical potential and show that the finite-volume corrections to the low-energy constants $\Sigma$ and $F$ for the partially quenched partition function, and hence for spectral correlation functions of the Dirac operator, are the same as for the unquenched...

Source: http://arxiv.org/abs/0909.1489v2

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Sep 22, 2013
09/13

by
R. V. Mishmash; I. Danshita; Charles W. Clark; L. D. Carr

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We present a fully quantum many-body treatment of dark solitons formed by ultracold bosonic atoms in one-dimensional optical lattices. Using time-evolving block decimation to simulate the single-band Bose-Hubbard Hamiltonian, we consider the quantum dynamics of density and phase engineered dark solitons as well as the quantum evolution of mean-field dark solitons injected into the quantum model. The former approach directly models how one may create quantum entangled dark solitons in...

Source: http://arxiv.org/abs/0906.4949v4

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Sep 18, 2013
09/13

by
Nick Gill; Anupam Singh

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We classify the real and strongly real conjugacy classes in $GL_n(q)$, $SL_n(q)$, $PGL_n(q)$, $PSL_n(q)$, and all quasi-simple covers of $PSL_n(q)$. In each case we give a formula for the number of real, and the number of strongly real, conjugacy classes.

Source: http://arxiv.org/abs/0809.4412v2

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Sep 22, 2013
09/13

by
Sourin Das; Sumathi Rao; Arijit Saha

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We study transport through a single channel t-stub geometry strongly coupled to a superconducting reservoir. In contrast to the standard stub geometry which has both transmission resonances and anti-resonances in the coherent limit, we find that due to the proximity effect, this geometry shows neither a T=1 resonance (T is the transmission probability for electrons incident on the t-stub) nor a T=0 anti-resonance as we vary the energy of the incident electron. Instead, we find that there is...

Source: http://arxiv.org/abs/0811.0660v4

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Sep 19, 2013
09/13

by
Amelia M. Stutz; George H. Rieke; John H. Bieging; Zoltan Balog; Fabian Heitsch; Miju Kang; William L. Peters; Yancy L. Shirley; Michael W. Werner

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We present Spitzer observations of a sample of 12 starless cores selected to have prominent 24 micron shadows. The Spitzer images show 8 and 24 micron shadows and in some cases 70 micron shadows; these spatially resolved absorption features trace the densest regions of the cores. We have carried out a 12CO (2-1) and 13CO (2-1) mapping survey of these cores with the Heinrich Hertz Telescope (HHT). We use the shadow features to derive optical depth maps. We derive molecular masses for the cores...

Source: http://arxiv.org/abs/0910.5476v2

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Sep 21, 2013
09/13

by
Hanfeng Li; Anthony Weston

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Doust and Weston introduced a new method called "enhanced negative type" for calculating a non trivial lower bound p(T) on the supremal strict p-negative type of any given finite metric tree (T,d). In the context of finite metric trees any such lower bound p(T) > 1 is deemed to be non trivial. In this paper we refine the technique of enhanced negative type and show how it may be applied more generally to any finite metric space (X,d) that is known to have strict p-negative type for...

Source: http://arxiv.org/abs/0901.0695v3

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Sep 22, 2013
09/13

by
Daniel Rudoy; Prabahan Basu; Patrick J. Wolfe

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In this article we introduce a broad family of adaptive, linear time-frequency representations termed superposition frames, and show that they admit desirable fast overlap-add reconstruction properties akin to standard short-time Fourier techniques. This approach stands in contrast to many adaptive time-frequency representations in the extant literature, which, while more flexible than standard fixed-resolution approaches, typically fail to provide efficient reconstruction and often lack the...

Source: http://arxiv.org/abs/0906.5202v2

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53

Sep 21, 2013
09/13

by
D. A. Perley; S. B. Cenko; J. S. Bloom; H. -W. Chen; N. R. Butler; D. Kocevski; J. X. Prochaska; M. Brodwin; K. Glazebrook; M. M. Kasliwal; S. R. Kulkarni; S. Lopez; E. O. Ofek; M. Pettini; A. M. Soderberg; D. Starr

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In this work we present the first results of our imaging campaign at Keck Observatory to identify the host galaxies of "dark" gamma-ray bursts (GRBs), events with no detected optical afterglow or with detected optical flux significantly fainter than expected from the observed X-ray afterglow. We find that out of a uniform sample of 29 Swift bursts rapidly observed by the Palomar 60-inch telescope through March 2008 (14 of which we classify as dark), all events have either a detected...

Source: http://arxiv.org/abs/0905.0001v3

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51

Sep 19, 2013
09/13

by
M. A. Prieto; J. Reunanen; K. R. W. Tristram; N. Neumayer; J. A. Fernandez-Ontiveros; M. Orienti; K. Meisenheimer

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Spectral energy distributions (SEDs) of the central few tens of parsec region of some of the nearest, most well studied, active galactic nuclei (AGN) are presented. These genuine AGN-core SEDs, mostly from Seyfert galaxies, are characterised by two main features: an IR bump with the maximum in the 2-10 micron range, and an increasing X-ray spectrum in the 1 to ~200 keV region. These dominant features are common to Seyfert type 1 and 2 objects alike. Type 2 AGN exhibit a sharp drop shortward of...

Source: http://arxiv.org/abs/0910.3771v3

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35

Sep 22, 2013
09/13

by
H. -M. Guo; M. Franz

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Electrons hopping on the sites of a three-dimensional pyrochlore lattice are shown to form topologically non-trivial insulating phases when the spin-orbit (SO) coupling and lattice distortions are present. Of 16 possible topological classes 9 are realized for various parameters in this model. Specifically, at half-filling undistorted pyrochlore lattice with SO term yields a 'pristine' strong topological insulator with Z2 index (1;000). At quarter filling various strong and weak topological...

Source: http://arxiv.org/abs/0908.0698v2

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32

Sep 21, 2013
09/13

by
Dibyendu Roy

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We study two simple mesoscopic models of interacting two electrons; first one consists of two quantum coherent parallel conductors with long-range Coulomb interaction in some localized region and the other is of an interacting quantum dot (QD) side-coupled to a noninteracting quantum wire. We evaluate exact two-particle scattering matrix as well as two-particle current which are relevant in a two-particle scattering experiment in these models. Finally we show that the on-site repulsive...

Source: http://arxiv.org/abs/0905.3881v2